summer swim team

Question
Hi,
My son is 10 years old and has been swimming with a year round team since September. He is really loving the sport and his coach says he is progressing rapidly-- they just moved him to a new practice group. Right now they are training for the long course season.

For summer, he will be with a different recreational team and only swimming 25 yard events. While, my son seems in the upper tier for 50s and 100s on his year round team, his 25 yard sprints don't seem any faster than last summer. (before training). Is there something he should do differently to train for the short sprints of the summer? Will training for long course on the year round team-- interfere with sprinting for the summer team?

Also- will it be more advantageous for him to stay underwater for the 25 yard races--- how far are they allowed to go underwater for rec. swimming?

Please know, that I ask not as a competitive parent. He wants to see improvement from summer to summer.

Answer
Susan--The best thing he can do to maintain his sprint speed is to finish each workout with a set of 5 to 10 sprints(if they are in a 50m. pool, only go 25m at full sprint, working on starts and initial speed coming up).  The long course training will benefit him in the long run(building endurance), and it shouldn't interfere with summer leagues.  Just remind him to always concentrate on his turns, so they are as technically correct as possible for any short course racing.  Most rec. leagues follow the US swimming rules pretty close, but double check on the rules also.  The rule I beleive is 15yds./ms. underwater.  As long as his streamline and kick underwater aren't slowing him down, use the rule to his advantage.  If he isn't maintaining his speed long enough, he needs to come up earlier.  
At 10 years old, he really doesn't have much time left swimming 25's, so I wouldn't be too concerned as long as his other events are still strong.  Most importantly, keep it fun.  If it's not fun it's hard to stay into the sport.
Hope this helps.
George